Studies will be conducted to elucidate the developmental interrelationships of putative neurotransmitters in the rat brain. The metabolism of putative neurotransmitters will be altered at specific periods of neurochemical naturation during gestational or neonatal stages. This will be accomplished in three ways: (1) by placement of discrete lesions in the nuclei of origin of neurons containing dopamine, norepinephrine, serotonin, acetylcholine or gamma-amino butyric acid in 4, 10, 21 and 39 day old rats; 2) with the use of drugs (e.g., chlorpromazine, amphetamine, benztropine and apormorphine) that are known to act by altering the activity of neurons containing biogenic amines or their receptors and 3) by neonatal administration of 6-hydroxydopamine. The hypothesis that the manipulation of biochemical and morphological differentiation during gestational or neonatal stages of growth has long-lasting and permanent consequences on normal neurochemistry of brain will be tested.